Hi, my 1st post and I'm asking around elsewhere as well....

OK, here's the deal. 1990 L98 133K miles

1st...I'm a licensed aircraft mechanic with about 20,000+ heavy maintenance hours on helicopters and fixed wing so I know my way around tools and stuff and I work on my car just like I would an aircraft, I have my tech manual open and I tag my parts...nuff said

I had a suspicion that the throttle body on my '90 L98 had never been cleaned and I was correct, it looked like it had bits of charcoal down its throat and when I removed it the backside looked like the darkside surface of the moon.

I cleaned the throttle body as described in "101 Projects for your Corvette 1984-1996" by using spray throttle body cleaner and a soft toothbrush and paintbrush...no scraping, scratching or anything like that. I also cleaned the ports on the plenum and they turned from dark brown/black to pretty aluminium.

I reinstalled with a new gasket of course (18 inlbs torque), hooked up the vacuum and water lines so on and so forth. Double and tripple checked connections.

The thing runs like a log wagon....Loping at idle and no power especially when trying to go into passing gear on the road...falls flat on its fanny...Oh yeah...fuel pressure 36-37 lbs at idle and open throttle.

Before I did this the thing would snap your neck going into passing gear and it was smooth at idle

 

Air, spark, and fuel. Check for vacuum leaks, codes, good connection for your distributor harness (aka EST and would show a code if unplugged), and fuel. (The EST connector links communication from the ECM to your dizzy. Advance is electronic on these cars.)

You already know fuel is a PROBLEM. Pressure is supposed to be 6-7PSI higher -- unless your yr is different than mine. Check what your FP is supposed to be. If it's supposed to be 43.5,,,there's the issue.

You don't want to be running it lean very long -- esp if you're getting any lean miss (spark miss).

 

Good advise here.

 

So it ran fine before you cleaned you TB, correct ? Then I think your fuel pressure is not the problem.

When you had the TB off, did you remove the IAC and clean it seperately, as well as the IAC passage ? When cleaning the IAC, it is recommended to hold it with pintl facing down, and ONLY spray the pintle and shaft.

You need to be careful cleaning the IAC and not get TB cleaner/solvents inside. The IAC is an electrical stepper motor and you do not want TB cleaner sliding down the pintle into the motor housing.

 

by chance, did you move the throttle position sensor? did you get any gum, varnish in the connector?

 

Nope, didn't touch it.

My IAC was dark black and nothing moved, wiggled or anything else when I removed it, could that be a problem?